The invention relates generally to the field of digital data processing systems for distributed monitoring and control in industrial environments, and in particular to a compact, modularly expandable controller (called herein a "field controller") and internal dongles adapted for use with the controller.
Distributed control systems are often used in a number of commercial, industrial and home applications, in particular to monitor and control operations at manufacturing, chemical processing and similar industrial operations, to monitor and control environmental and other factors and so forth. In a manufacturing operation, a distributed control system will typically control machines which facilitate the manufacture and assembly of the products being manufactured. In addition, in a chemical processing operation, a distributed control system may control valves to control rates of flow of chemicals into and out of reaction chambers, and monitoring and/or controlling reaction temperatures and pressures and the like which are required to carry out the chemical process. In addition to controlling the manufacturing or chemical process, distributed control systems may perform bookkeeping operations to keep track of the inventory of inputs required for the manufacturing or chemical process, as well as the inventory of outputs produced by the operation. Typical distributed control systems essentially comprise large, centrally-located and expensive computer systems, which can be expensive to maintain and typically have limited expansion capabilities.
A control system may include one or more PCMCIA cards that each couple to a device in the industrial environment, such as, for example, an instrument, monitor, machine or the like. Often, it is advantageous to include an active or passive circuit in the coupling between the controller and the device. The cable may include the circuit. In one arrangement, called a "dongle," the cable has an encapsulated end portion that includes the active or passive circuit and a connector.